Crown ethers are macrocyclic compounds in which oxygen atoms are separated by two or three carbon atoms. The name has been used for this class of compounds because of the resemblance of their molecular models to a crown. Since their discovery in the late 1960's, crown ethers have been intensively studied because of their cation complexing and binding abilities, especially to alkali and alkali earth cations. Crown ethers and compounds containing crown ethers are useful for a variety of applications, such as metal ion chelating and binding agents, catalysts for phase transfer reactions, encapsulating materials for electronic devices, and corrosion inhibitors in electronic packages and electrorheological fluid. Crown ethers are known to be useful as complexing agents for alkali and alkali earth cations, but are not particularly effective for complexing transition metal cations.
Thiacrown ethers are crown ethers in which the oxygen atoms are replaced with sulfur atoms as shown in Formula 1. ##STR1##
In contrast to the crown ethers, few applications have been explored for thiacrown ethers and their derivatives, although they are reported to form strong complexes with transition metal ions such as Cu.sup.+2, Fe.sup.+2, Ni.sup.+2, Co.sup.+2, Hg.sup.+2 and Ag.sup.+.
Due to increasingly stringent environmental regulation, the trend in industry has been to emphasize water reuse and recycling in order to minimize the discharge into the environment of water containing undesirable materials. Depending on the industrial system, it is often desirable to treat used process water to remove materials such as metals prior to recycling water or prior to discharging the used process water to the environment. In addition, in some industries such as in the photo developing industry, metals such as silver are valuable components which are typically recovered from used process streams prior to water discharge.
Thus, there is an ever present demand for new and efficient metal removal materials to facilitate the removal of metals from process streams prior to reuse or discharge.
Accordingly, an object of this invention to provide thiacrown ethers, polymeric thiacrown ethers to fulfill the desire for new and effective metal ion chelating, sequestering, and complexing agents and corrosion inhibitors.